internal/cpu: add support for x86 FMA cpu feature detection

Change-Id: I88ea39de01b07e6afa1c187c0df6a258da4aa8e4
Reviewed-on: https://go-review.googlesource.com/62650
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/internal/cpu/cpu.go

@@ -20,6 +20,7 @@ type x86 struct {
 	HasBMI1      bool
 	HasBMI2      bool
 	HasERMS      bool
+	HasFMA       bool
 	HasOSXSAVE   bool
 	HasPCLMULQDQ bool
 	HasPOPCNT    bool

src/internal/cpu/cpu_x86.go

@@ -27,6 +27,7 @@ func init() {
 	X86.HasSSE3 = isSet(0, ecx1)
 	X86.HasPCLMULQDQ = isSet(1, ecx1)
 	X86.HasSSSE3 = isSet(9, ecx1)
+	X86.HasFMA = isSet(12, ecx1)
 	X86.HasSSE41 = isSet(19, ecx1)
 	X86.HasSSE42 = isSet(20, ecx1)
 	X86.HasPOPCNT = isSet(23, ecx1)